Question: Expand and combine like terms. $(4m^5-5m^6)(4m^5+5m^6)=$
Explanation: We can expand this expression like any product of two binomials. However, this expression has a special form that makes it easier to expand. This is the "difference of squares" form (where $P$ and $Q$ can be any monomial): $(P+Q)(P-Q)=P^2-Q^2$ $\begin{aligned} &\phantom{=}(4m^5-5m^6)(4m^5+5m^6) \\\\ &=\left(4m^5\right)^2-\left(5m^6\right)^2 \\\\ &=16m^{10}-25m^{12} \end{aligned}$